The present invention relates to instant on/off switches for controlling medical and dental instruments and in particular to a switch that is adapted to automatically energize an instrument when the instrument is removed from its holder.
Medical and dental opertory units typically have numerous electrically operated instruments that rest in holders located on the unit. The holders or "cradles" act as instant-on switches and are generally spring-biased against the weight of the instruments so that when an instrument is removed from its holder, the cradle pivots upward actuating a switch which energizes the instrument. This arrangement is similar to that utilized for the receivers on most wall-mounted telephones. The disadvantage with this arrangement, however, is that a relatively expensive spring-activated microswitch is required which must be hand-wired and mounted inside a plastic box situated within the unit. In addition, the need for a separate microswitch in the unit constrains the position of the instrument holder to a location on the unit that is accessible for wiring purposes. Moreover, the existence of numerous spring-actuated microswitches in a unit increases the complexity of the wiring harness for the unit.
The present invention seeks to overcome these disadvantages by providing an instant-on switching arrangement that eliminates the need for a spring-actuated microswitch. In addition, in the preferred embodiment of the present invention, the need for an internal switch which must be separately wired is eliminated completely. Thus, the complexity of the wiring harness required for the unit is significantly reduced.
The present invention accomplishes these results by providing a magnetically-actuated switch that is incorporated into the handle of the instrument and is electrically connected in series with the instrument load. A permanent magnet is embedded in the instrument holder. When the instrument is in the holder, the proximity of the permanent magnet to the magnetically-actuated switch in the handle of the instrument maintains the switch in its open condition, thereby cutting off electrical power to the instrument. When the instrument is removed from the holder, however, the absence of the magnetic field closes the switch in the handle of the instrument, thus energizing the instrument. Moreover, when the instrument is returned to its holder, the instrument is again automatically de-energized.
Additional objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment which makes reference to the following set of drawings in which :